Elsevier

Physiology & Behavior

Volume 77, Issues 4–5, December 2002, Pages 477-482
Physiology & Behavior

The anterior cingulate as a conflict monitor: fMRI and ERP studies

https://doi.org/10.1016/S0031-9384(02)00930-7Get rights and content

Abstract

We propose that the anterior cingulate cortex (ACC) contributes to cognition by detecting the presence of conflict during information processing, and to alert systems involved in top-down control to resolve this conflict. Here, we review several functional magnetic resonance imaging (fMRI) and event-related potential (ERP) studies that have used simple response interference tasks, and propose that ACC activity is activated prior to the response during correct conflict trials and reflected in the frontocentral N2, and immediately following error trials and reflected in the error-related negativity (ERN). Furthermore, we suggest that certain disturbances in cognition and behavior in common mental disorders such as schizophrenia and obsessive-compulsive disorder (OCD) can be understood as resulting from alteration in performance monitoring functions associated with this region of the brain.

Introduction

The anterior cingulate cortex (ACC), located on the medial surface of the frontal lobes, has been the subject of increasing interest during the previous decade. It is usually thought of as playing an important role in attentional and motivational processes [1]; however, its exact role in cognition has been the subject of debate. We have recently proposed a comprehensive theory of human ACC functioning that we believe accounts for most, if not all, of the neuroimaging and event-related potential (ERP) data available about this region of the brain [2], [3]. According to this view, the ACC is activated in response to conflict occurring between incompatible streams of information processing. Following conflict detection, regions of the lateral prefrontal cortices and other areas associated with attentional control are engaged to resolve the conflict. The current review will focus on discussing evidence supporting the conflict theory. In particular, we focus on data obtained using two methodologies from modern cognitive neuroscience that we have used to test predictions of this theory: functional magnetic resonance imaging (fMRI) and ERPs. fMRI has excellent spatial resolution but relatively poor temporal resolution, while ERPs have excellent temporal resolution but relatively poor temporal resolution. The two methodologies are thus mutually complementary in developing a spatio-temporal map of human brain activity during cognition.

Section snippets

fMRI studies of ACC functioning

An earlier, popular view of ACC functioning maintained that it was involved in exerting attentional control and selection for action [4]. According to this view, the ACC guides the selection and processing of stimuli that need to be acted upon or are otherwise relevant to the currently active task or goal representation. In contrast, we maintain that ACC activity is often observed when control is engaged because a strong engagement of control is needed in situations in which conflict is high [3]

ERP correlates of ACC activity

Another popular theory of ACC functioning was based on research using ERPs. In the presence of response conflict, people are known to sometimes make fast, impulsive errors based on partial, incomplete analysis of the stimulus. Such impulsive errors are known as “slips” [17]. Research has shown that within 50–150 ms following the commission of a slip, a large, negative deflection is observed in the ERP, with a maximum at frontal or central sites [18], [19]. Subsequent dipole modeling of this

Implications for neuropsychiatric disorders

Disturbances in the function of the ACC have been reported in a number of psychiatric disorders, including schizophrenia and obsessive-compulsive disorder (OCD). In schizophrenia, cognitive control is impaired, and the level of cognitive dysfunction in the illness is correlated with behavioral disorganization and with social and occupational disability [37]. The conflict monitoring theory of schizophrenia would predict that if ACC dysfunction is contributing to these deficits, decreases in both

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